Within the floorcoverings industry there is constant demand for yarns that can be woven, knitted or tufted into backing materials that exhibit novel and aesthetically pleasing appearance. In particular, yarns that, when incorporated into carpets, produce random or irregular color changes over a flooring area are very popular.
Space-dyed yarns are traditionally made via a process that involves dyeing yarns to create the effect of the color varying at irregular intervals along the length of the yarn, for example by knit-de-knit or warp printing. Such produced space-dyed yarns can produce a variety of visually appealing effects in carpets. Including well differentiated color points in an unorganised design. However, the processes are slow and inefficient, adding to the high cost of such products, and the dyeing process itself has environmental drawbacks.
Another approach to obtaining novel color effects in a yarn is to combine two or more yarns, hereinafter referred to as singles yarns, into a yarn bundle, hereinafter referred to as the product yarn. In the case where at least one singles yarn differs in color or dyeability from the others, product yarns with a wide variety of effects may be manufactured.
Heather yarns are created by entangling singles yarn individually and collectively, at chosen levels of entanglement, to provide a range of color effects. Heather yarns can, when incorporated into a carpet, produce color effects ranging from well-blended yarns in which a single color is perceived at normal viewing distance from the floor, to various degrees of speckled appearance, when random points of color can be differentiated by the observer at the normal viewing distance. Yarns that come under this category do not feature the same degree of color differentiation as space dyed yarns.
In order to produce yarns that can provide similar aesthetics to space dyed yarns, more sophisticated entanglement processes have been developed for the manufacture of yarns referred to as “mock” or “apparent” space dyed. See, for example U.S. Pat. No. 5,804,115 (Burton et al), and U.S. Pat. No. 6,240,609 and U.S. Pat. No. 6,401,315.
Other approaches to the manufacture of yarns with a similar appearance to space dyed yarns have been made.
U.S. Pat. No. 6,023,926 (Flynn) describes a yarn and process in which two or more singles yarns, where at least one singles yarn differs in color from the others, are false-twisted together at low false twist level to produce a low frequency alteration of the predominant color along the length of the assembly. The false twist is then stabilised by helically wrapping the false-twisted bundle with a very low denier yarn, which itself does not visibly contribute to the appearance of the product yarn.
U.S. Pat. No. 6,536,200 (Schwartz) achieves a similar appearance by separately tensioning two differently colored singles yarns and combining these under controlled varying tension in such a manner that controllable lengths of the bundle show one color predominantly when the singles yarn of the first color is under low tension and the singles yarn of the second color is under high tension, and vice versa. Again, the bundle is helically wrapped with one or more very low denier yarns, or with monofilament(s).